1. Field of the Invention
The present invention generally relates to soil stabilization and more particularly to stabilizing active soils at building sites that are subject to significant shrinking and swelling due to variations in moisture content.
2. Background of the Invention and Description of the Prior Art
Shrinking and swelling of soil upon which a building foundation is constructed is a well-known problem in the building industry particularly for residential structures. Soils such as clay, for example, that have a relatively high plasticity index, often termed “expansive soils,” typically lack sufficient stability to avoid foundation damage due to moderate or wide variations in the moisture content of the soil upon which the foundation is constructed. In a typical slab foundation with a perimeter grade beam, which surrounds the perimeter of the slab, the moisture content of the soil inside the perimeter grade beam can vary substantially from the moisture content of the soil outside the perimeter grade beam. This is because the outside soil is subject to widely varying amounts of moisture due to cycles of rainfall or lack thereof throughout the seasons of the year, while the soil within the perimeter grade beam is isolated from such moisture variations.
A substantial variety of businesses have been active and successful over the years in responding to the need for remediation of the conditions that cause foundation shifting, cracks, masonry cracks in the building veneer, cracks in the interior walls of the structure, doors that won't close properly, plumbing systems that develop leaks, etc., all due to shifts on the soil upon which the building foundation is constructed. Many of these remedies involve construction of foundation supports to level the foundation, to provide support down to more solid subsurface components, to provide auxiliary supporting posts, beams, and the like to provide a stronger foundation less susceptible to flexing, cracking, and the like. Other kinds of remedies may involve providing injection of chemicals or fluids into the soil, or controlled moisture or irrigation systems to provide a more uniform moisture content year-round.
Such remedies tend to be expensive and are often subject to individual skills or techniques used in a particular situation. Some are satisfactory over the long term life of the structure; others must be rebuilt or replaced with other remediation countermeasures. What is needed is a solution to the problem that is provided at the time the foundation is initially constructed or that is inherent in the design of the foundation. A solution that prevents damage to a foundation regardless of the moisture variations that occur in the soil it is built upon would minimize damage to structures built on the slab foundation and negate future needs to reconstruct the foundation or to later install countermeasures to correct this troublesome problem.